1. Field of the Invention
The present invention relates to a microscope, and more particularly to an improved focus-adjusting mechanism for use in a microscope.
2. Description of the Related Art
Various focus-adjusting mechanisms are used in microscopes. Four microscopes, each having a focus-adjusting mechanism, will be described with reference to FIGS. 9 to 12.
The microscope shown in FIG. 9 comprises a main unit 1, a lens barrel 3, a revolver 4, and an objective 5. The main unit 1 has an arm top 2 and arm body 6. The barrel 3 is connected at its lower end to the arm top 2 and has an eyepiece 3a fixed to its upper end. The revolver 4 is also connected to the arm top 2. The objective is fixed to the revolver 4. The eyepiece 3a and the objective 5 are placed in the same viewing axis. The microscope further comprises a movable support 7, a stage 8, a stage holder 9, a focus adjustment knob 10, and a focus-adjusting mechanism (not shown). The movable support 7 is mounted on the front of the arm body 6 and can slide up and down, in parallel to the viewing axis. The stage 8 is held by the holder 9, which is fastened to the support 7. The focus adjustment knob 10 is mounted on one side of the arm body 6. The focus-adjusting mechanism is housed within the arm body 6 and connected to the, focus adjustment knob 10. In operation, a specimen S is put on the stage 8 and placed on the viewing axis. Then, the knob 10 is rotated, thus driving the focus-adjusting mechanism. The focus-adjusting mechanism moves the support 7 vertically. As a result, the stage 8 is moved up or down, bringing the specimen S to the focal point of the objective 5.
The microscope shown in FIG. 10 is characterized in two respects. First, the stage holder 12 is immovably secured to the main unit 11. Second, the focus adjustment knob 10 and the revolver 13 are coupled to the focus-adjusting mechanism 14 housed within the main unit 11. Hence, as the knob 10 is rotated, the revolver 13 having an objective is moved vertically, whereby the focal point of the objective is moved to the specimen S.
The microscope shown in FIG. 11 is characterized in that the arm top 16 is slidably attached to the arm body 15 of the main body 1. As the focus adjustment knob 10 is rotated, the arm top 16 is moved up or down, whereby the focal point of the objective is moved to the specimen S.
The microscope shown in FIG. 12 is identical to the microscope of FIG. 11, except for in three respects. First, a fixed support 17 containing an auxiliary focus-adjusting mechanism (not shown) is fastened to the main unit 1. Second, an auxiliary focus adjustment knob 19 is mounted on one side of the support 17 and connected to the auxiliary focus adjustment mechanism. Third, the stage holder 18 is slidably attached to the fixed support 17 and driven by the auxiliary focus-adjusting mechanism. Hence, the objective and the stage are independently moved vertically when the knobs 10 and 19 are rotated.
In the microscope shown in FIG. 9, the stage 8 can have but limited size and rigidness since it is supported by a pole guide or a roll guide and is moved vertically to accomplish focus adjustment. Hence, the stage 8 cannot support a relatively heavy specimen, and is likely to be deformed, which results in various problems in microscopic observation.
The microscope shown in FIG. 10, wherein the objective is moved up and down to achieve focusing, is disadvantageous. The distance between the objective and the lens barrel 3 is long unless the objective is an infinity type. Consequently, various optical deteriorations such as insufficiency of ambient light occur, making it impossible for the microscope to have an adequate focusing stroke.
In the microscopes shown in FIGS. 11 and 12, the arm top 16 can have but limited rigidness since it is moved vertically to effect focus adjustment. Thus, it would be impossible to mount a camera on the top arm.